Certain applications of magnetic core stacks require that the stacks be sufficiently rugged so as to withstand substantial vibration. Such applications include use in moving vehicles, both military and others, and various airborne vehicles such as aircraft, spacecraft and missiles.
Magnetic core stacks which are subjected to vibration may fail for various reasons. Stacks which are not reinforced with stiffening elements, particularly those with high mass, typically have a low natural frequency at or close to the frequencies of typical vibrations. Under such conditions the stacks can easily resonate at their natural frequency and quickly fail if the vibrations have sufficient amplitude. As a consequence military and other specifications relating to magnetic core stack applications involving mechanical vibration typically require the stack for such applications to be stiffly constructed or reinforced so as to have substantial vibration resistance.
A common approach to the problem of designing a vibration-resistant core stack has been to add considerable sttiffness to each individual layer of the core stack. The individual layers in such stacks are typically separated by a substantial distance to prevent the cores in adjacent layers from contacting one another. Each individual layer of the cores is stiffened by a thick piece of aluminum or other material of sufficient stiffness. The result is that as each layer of the stack is provided with increased stiffness and greater separation from adjacent layers, the mass and volume of the stack increase significantly. Consequently, while the individual layers are themselves highly resistant to vibration, the composite structure of the system has a low natural or resonant frequency so as to render the stack highly susceptible to damage or failure in addition to being relatively heavy and consuming considerable space.